12

My biology teacher told me that if one caught HIV, they cannot be cured because it was near to impossible to be completely virus-free. She said this was because HIV keeps on changing its glycoprotein coat.

Can someone please explain what she meant by "keeps on changing its glycoprotein coat" to me?

AMR
  • 5,005
  • 1
  • 19
  • 38
  • I have an exam tomorrow and i am thoroughly confused. –  Oct 05 '15 at 16:48
  • 4
    There is a huge difference between "not cured yet" and "incurable." Have you done any research to answer this question yourself? – MattDMo Oct 05 '15 at 17:31
  • 3
    Seems a bit harsh to down vote a question coming from someone's teacher. The student can't really be held responsible for using the teacher's bad wording. At least they're seeking the right answer. – Nathan Oct 05 '15 at 20:08
  • I think this is a valuable, albeit broad, question. @Amory has answered the question well with an appropriate amount of detail. – James Oct 05 '15 at 21:39
  • 3
    @MattDMo, if you want to nitpick about not cured yet versus incurable, then I think Amory's point that incurable is a misnomer is valid. You cannot cure a virus. You can cure the infection that they virus causes by neutralizing the virus, but it isn't the virus that is being cured, it is the infection. So the title should really read, Why is an HIV infection incurable? Actually would be is probably better. So Why would an HIV infection be incurable? And the biology teacher is probably just hedging her statement because of The Berlin Patient. Actually I will edit for accuracy. – AMR Oct 06 '15 at 02:45
  • @AMR I won't speak for MattDMo but I for one am being pedantic in a different way that you are. I think saying "virus/bacteria can't be cured, infection can" is unnecessarily pedantic; my personal pedanticism is rather "we're just not there yet." At any rate, I think your edit actually changed the question to much and isn't even quite right - depending on your definition of "virus," there's more to being "cured" than being virus free – Amory Oct 06 '15 at 13:15
  • @Amory HIV isn't the disease. By virus free I meant that all of the reservoirs in the body were also eradicated. We have only done it with the Berlin Patient... And HAART, technically can be a cure if you do not define a cure as no longer requiring treatment and will no longer be affected by the virus. It turns terminal into chronic, which many are willing to live with. – AMR Oct 06 '15 at 13:52
  • @AMR That's sort of my point. You changed "incurable" to "completely virus-free" which aren't necessarily the same thing, nor necessarily what was meant. – Amory Oct 06 '15 at 14:12
  • @Amory fair enough... It was late and I wasn't thinking in terms of making all remaining proviruses transcriptional inactive, though tat would likely require maintenance treatment, meaning it isn't a cure. This is peer review, if you do not agree with my edit, then submit your edit to mine. With HIV, however, would be inclined to say that cure necessarily entails being virus free. Because even one cell, hat boring a provirus can lead to AIDS if it becomes transcriptionally active.... Unless you can do what happened to the Berlin Patient, and all new immune cells do not have the coreceptor. – AMR Oct 06 '15 at 14:47

2 Answers2

18

The reasons why HIV is "incurable" (a misnomer) are legion:

  • HIV is a retrovirus, which means it inserts its own genome into the host cell's genome. You must therefore kill each and every infected cell to rid the body of the virus.
  • HIV is a lentivirus, which means it has a long incubation period, so it can "lay low" before symptoms are readily detected.
  • HIV infects CD4+ helper T-cells, macrophages, and dendritic cells, which are responsible for mediating the host immune response. Thus, it infects specifically the cells we need to fight an infection.
  • HIV drastically reduces the number of CD4+ T-cells.
  • HIV has a number of viral proteins that prevent some of the body's antiviral mechanisms
  • HIV can infect via cell-free (large number of particles, low infection rate) or cell-to-cell (low number of particles, high infection rate) routes.
  • HIV is wildly variable. It has a small RNA genome (about 10kb) that mutates very rapidly. Given the number of viral particles produced each day during infection — well over 1 billion — every single base is mutated every day.

I'm simplifying matters a bit — you should just read the en.Wikipedia article for your own research — but that's a rundown of some of the reasons why.

Amory
  • 9,681
  • 2
  • 44
  • 61
  • 3
    This is a very neat answer for quite a complex question. Very nice! – James Oct 05 '15 at 21:30
  • Nice answer. Your first two points answer the question. A few things you can add. Dendritic cells are the only APCs that can activate naive T-Cells (your cell-to-cell route) but the fact that it is in DCs makes it more insidious. HIV can cause CD4 death in 3 major ways. 1)Apoptosis. integrase causes ds breaks which triggers cell death. 2)Recognition by CD8 cells. 3)Though lysogenic, with enough budding, infected cells will not have enough membrane and they lyse. Also the variability you mention often changes tropism and allows gp120 to have affinity for coreceptors other than CCR5 and CXCL4. – AMR Oct 06 '15 at 02:33
  • @AMR "Simplifying matters a bit" ;-) – Amory Oct 06 '15 at 13:16
  • It is good enough to be a reference answer, so I thought might as well make it more complete. – AMR Oct 06 '15 at 13:41
  • I think the second bullet point suggests a conclusion that may not be readily apparent to a lay reader: a second sentence to the effect of “Thus, there are already a lot of cells to kill even if treatment begins as soon as symptoms appear.” The second-to-last bullet also seems like it needs to state what its significance is: is one or both of these routes unusual or particularly problematic, or is it just that having both in one virus that is notable? – KRyan Apr 04 '16 at 20:34
-1
  1. HI virus attaches itself to the CD4 cells making it diffuclt for the body to destory it own cells.
  2. the virus mutates faster and keep changing it shape
Chris
  • 51,604
  • 13
  • 119
  • 176
benja
  • 1